Properties of the body of a turbidity current at near‐normal conditions: 2. Effect of settling

Abstract

Turbidity currents are sediment-laden flows that move over a sloping surface. These flows are driven by the density difference between the sediment-laden current and the clear ambient fluid above. Here we focus on studying the process of ambient fluid entrainment at the interface between the current and the sediment-free ambient fluid and obtain a closure model for the entrainment coefficient. In particular, we extend the classical dependence of entrainment coefficient on the bulk Richardson number, by including the effect of sediment settling velocity. We focus our attention to turbidity currents under normal flow condition, where the depth-averaged streamwise velocity U is nearly a constant. We employ direct numerical simulations of temporally evolving turbidity currents. Similarly, we study the dependence of basal drag distribution on Richardson number and settling velocity. In addition, we study the turbulence structures of the flow and its relation to turbulence production.